Microfibrous fabric having a suede appearance, within the colour range of grey and black, with a high light fastness, and preparation method thereof

ABSTRACT

A high-quality artificial leather is described, having a suede appearance and colors within the grey-black range, the light fastness of the colors according to the method SAE J 1885 225.6 KJ/m 2  being higher than or equal to 4; the lightfastness of the colors according to the method SAE J 1885 488.8 KJ/m 2  being not lower than 3; said artificial leather having a tassel on the surface of the leather itself. The average length of the tassel is between 200 and 500 microns. The soft segments consist of at least one polycarbonate diol selected from polyalkylene carbonate diols and at least one polyester diol; the hard segments consist of urethane groups deriving from the reaction between free isocyanate groups and water; and the total content of carbon black is between 0.025 and 6% by weight.

This application is a continuation of U.S. patent application Ser. No.16/434,756, filed Jun. 7, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/469,063, filed Mar. 24, 2017, now U.S. Pat. No.10,351,993, which is a divisional application of U.S. patent applicationSer. No. 12/993,213, filed Nov. 17, 2010, which a 35 U.S.C. § 371national-stage of International PCT Application No. PCT/IT2008/000739,filed Dec. 3, 2008, which claims priority to Italian Patent ApplicationNo. MI2008A001055, filed Jun. 10, 2008, all of which are hereinincorporated by reference in their entirety.

The present invention relates to a high-quality artificial leather,having a suede appearance and colours within the range of grey andblack, characterized by an high colour fastness when exposed to lightand a long durability, destined for use in car interiors.

The definition “high fastness” means high resistance of the colour shadeto undergoing variations following prolonged exposure to light.

The definition “high durability” means high resistance of the suedeleather, capable of lasting for long periods of time, even followinglong and repeated exposure to light and particularly oxidizing and/orhydrolyzing environments.

The process necessary for producing artificial leather with a highfastness is also part of the present invention.

The synthetic leather with a suede appearance, object of the presentinvention, even if characterized by the properties of high fastness tolight and a long durability, can be compared, in its most generalcharacteristics, to already known composite structures consisting of asurface having a high microfibre density and a matrix of the elastomerictype binding the same microfibre structure. The methods already used forthe production of high-quality synthetic leathers having a suede effect(see, for example, EP-A-0584511, EP-A-1323859, U.S. Pat. Nos. 7,144,535,3,531,368, 3,716,614) are all characterized by a process which can beschematized as follows:

-   A1) Spinning of a bi-component fibre of the “sea-island” type, in    which the “island” component consists of a polyester and/or    polyamide and the “sea” component of a polymer immiscible in the    island component and capable of dissolving in suitable solvents of    an organic or inorganic nature. The micro-fibres obtained after    dissolution of the sea component have counts typically lower than    0.5 dtex.-   A2) Preparation of a felt characterized by well-defined density    values and a unitary weight, by means of a mechanical needling    process capable of connecting the microfibres obtained in item A1.-   A3) Impregnation of the felt with a binder capable of withholding    the “islands” during the subsequent elimination phase of the “sea”    component. Said binder, which also has the function of suitably    reinforcing the felt to such an extent as to allow its immersion in    the solvent used for eliminating the “sea”, can be of two different    typologies.    -   The first is typically based on polyvinyl alcohol, which is        removed in a subsequent step of the process.    -   The second is typically based on polyurethane which partially or        totally remains in the final product, even after the subsequent        process steps.-   A4) Dissolution of the “sea” component in a suitable organic    (generally trichloroethylene) or inorganic (acidic or basic aqueous    solution, or simply in hot water) solvent to give the microfibrous    material.-   A5) Impregnation of the above-mentioned microfibrous material with a    polyurethane (PU) solution in organic solvents (dimethyl formamide,    DMF); as an alternative, said impregnation can be effected with    polyurethane in emulsion or aqueous dispersion (PUD).-   A6) Elimination of the binder used in point A3 if the binder is not    PU or PUD and of the solvent possibly used in step A5.-   A7) The microfibrous material impregnated with polyurethane is cut    into two equal portions, by means of a longitudinal cut, parallel to    the surfaces.-   A8) Grinding of the surfaces of the product by means of suitable    treatment with abrasive papers, in order to confer the suede    appearance to the structure.-   A9) Final dyeing of the product.-   A10) Finishing treatment (coupling with other substrates, printing,    etc.).

With reference to the dyeing process, it should be pointed out that themethods generally used for dyeing non-woven fabrics based on polyester,include dyeing the micro-fibrous component (tassel) by immersion of thematerial in baths containing dyes of the “dispersed” type. The use ofdispersed dyes only, does not require any dyeing of the polyurethanematrix which therefore maintains its original colour as it cannot besolidly dyed using this group of dyes. The dyeing process is concludedby a reducing cleaning step carried out by means of sodium hydrosulphitein NaOH, with the aim of removing the excess of dyes still present andunfixed on the material.

The colouring difference between tassel and polyurethane matrix isnormally critical, as the visibility of the background influencesnegatively the aesthetical impact of the final product.

In order to minimize the above-mentioned colour difference betweentassel and polyurethane matrix, various countermeasures are normallyadopted:

-   -   addition of organic or inorganic pigments to the polyurethane        itself, before the impregnation process;    -   resort to a second dyeing bath after the standard bath described        above, in which so-called “pre-metallized” dyes are used,        capable of dyeing the polyurethane base and thus limiting the        deterioration in quality attributable to the colour difference        (see patents IT 1097917, IT 1256230);    -   optimization of the tassel length, in order to find the correct        compromise between “coverage” of the PU background, imitation of        real suede leather and protection of the writing and mottling        effects: an excessively short tassel, in fact, it does not        reduce the visibility of the PU on the “noble” surface of the        product and decreases its qualitative level because it reduces        both two effects mentioned above.

With reference to the last aspect described, it should be noted that,due to its high surface density, the micro-fibrous component stronglycharacterizes the quality of the “visible” side of synthetic leatherswith a suede appearance, contributing, much more than the bindingmatrix, to the conferment of properties such as colour shade, mottling,the writing effect and soft feel, which represent the main parametersfor a qualitative evaluation of this type of non-woven fabric.

The products obtained as describe above, normally have some limits inthe invariability of the colour shade after light exposure. This limitedcolour fastness to light significantly conditions the applicativepotentialities, in particular to the field of car interiors, whichrepresents one of the reference markets for high-quality syntheticleathers which are widely used in the lining of car interiors.

For this reason, the colour fastness after exposure to light ofsynthetic leathers is carefully evaluated by means of various analyticalmethods which comprise the exposure of test samples to artificial lightsources under controlled irradiation and humidity conditions.

Unfortunately, there is currently no single analytical method for theevaluation of colour fastness to light and each car producer adopts aspecific method. Normally the various methods use Xenon lamps in orderto reproduce the solar irradiation spectrum as accurate as possible; theirradiation spectrum can also include radiations with wave-lengthsranging from 270 to 700 nm and the temperature of the exposure chambercan reach 60-70° C.

In Europe, the most widely-used methods are DIN 75 202 PV 1301, D47 1431and SAE J1885. In the USA market the most widely-spread method is FLTMBO116-01 in addition to SAE J1885. The following table shows the maintest conditions:

Black Chamber Exposure Method Apparatus Lamp panel temperature Humiditytime Irradiation DIN75202 Xenotest Beta Xenon 100 ± 2° C. 65 ± 5° C. 20± 10% 1, 2 and 3 60 W/m² PV 1303 (Heraeus) Fakra cycles 300 ÷ 400 nm D471431 Atlas CI3000 Xenon 100 ± 2° C. 66° C. + 2° C. 30 ± 10% 150 1.4W/m², (Heraeus) hrs 420 nm SAEJ1885 Atlas CI3000 Xenon light 62 ± 2° C.50 ± 5% 225.6 0.55 W/m², (Heraeus) 89 ± 2° C. 38 ± 2° C. 95 ± 5% KJ/m²340 nm dark 38 ± 2° C. light 62 ± 2° C. 50 ± 5% 488.8 0.55 W/m², 89 ± 2°C. 38 ± 2° C. 95 ± 5% KJ/m² 340 nm dark 38 ± 2° C. FLTM Atlas CI4000Xenon + light 62 ± 2° C. 50 ± 5% 451-902 1.06 W/m², BO116-01 auxiliary89 ± 2° C. 38 ± 2° C. 95 ± 5% KJ/m² 420 nm lamp dark 38 ± 2° C. light 62± 2° C. 50 ± 5% 942-3224 1.06 W/m², 89 ± 2° C. 38 ± 2° C. 95 ± 5% KJ/m²420 nm dark 38 ± 2° C.

The evaluation of the colour fastness to light is effected by comparingthe colour variation before and after exposure with the grey scale ISO105A02.

Various countermeasures are now adopted in order to maximize theresistance of the colour shade following exposure to light. One of themost common and efficient is to add organic or inorganic pigments to thepolymer used for the production of microfibres, upstream of the spinningphase (mass dye technology).

The mass dye technology does in fact allows the use of organic orinorganic pigments having a high fastness to light, which cannotnormally be applied in water bath dyeing.

For the classical dyeing of polyester, in fact, it is only possible touse organic dyes, dispersible in water, capable of being diffused insidethe polyester fibre. In the case of the dyeing of a polyestermicrofibre, it is necessary to provide of molecules having smalldimensions in order to obtain good dyeing yields in a short time.

The use of additional polymers with pigments in the spinning process,however, has also considerable drawbacks, such as:

-   -   increase in the obstruction process of the filtering screens        situated upstream of the spinnerets for protective purposes. The        acceleration of the obstruction phenomena implies an increase in        the frequency with which the filter screens must be substituted        and therefore a considerable increase in the production costs;    -   decrease in the mechanical properties of the micro-fibrous        component of the fibre with a consequent reduction of the        mechanical properties of the synthetic leather produced with it.

In order to limit the drawbacks listed, an accurate selection of thepigment used is necessary, with particular reference to the dimensionsof its particles and to its filterability, as well as the percentage ofits addition to the polymer. It should in fact be considered that higherpigment contents allow the production of synthetic fibres characterizedby deeper colour shades but they also imply more frequent obstructionsof the filtering systems positioned for the protection of the spinneretsand greater reductions in the mechanical properties of the same fibres.

The production of high-quality synthetic leathers therefore requires anoptimal compromise between the two mentioned factors, also resorting toalternative solutions, when necessary, for obtaining a certain colourshade. As the “overall” colour shade of a synthetic suede leather can beattributed to both the microfibrous (main) component and to thepolyurethane matrix, one of the possible known solutions for obtainingdark colours is to limit the micro-fibrous tassel length, so as to onlypartially cover the polyurethane base and to profit by the contributionof its “background” colour to obtain the desired colour shade (seepatent EP 1403421 in which the tassel length is from 10 to 200 μm). Theexpedient described above, however, has also serious drawbacks as itstrongly conditions the qualitative level of the synthetic leather dueto the limited writing and mottling effect obtained by means of areduced length of the tassel.

The measurement of the colour shade is normally carried out byinstrumental reading of the colour and by visual comparison with areference standard (mainly in the case of synthetic leather with a suedeappearance such as that object of the present invention). Instrumentsand reading techniques are well-known to experts in the field. The needfor a visual comparison is due to the different sensitivity of the humaneye with respect to the instruments on the market, but, above all, tothe specific surface of these types of materials which are characterizedby the presence of tassels, which leads the eye to perceive differentcolour shades according to the inclination of the microfibre withrespect to the observer. Several models have been prepared in order toreproduce, by means of instrumental analyses, the same colour perceptionof the human eye. One of the most simple and widespread is called CIELABsystem. This system is based on the representation of colours by meansof three coordinates defined by the letters L, a and b, arranged in aCartesian reference system. L represents luminosity and can have valuesfrom 100 (white) to 0 (black), whereas the other two coordinates (a, b),perpendicular to the former, identify the chromaticity of the colour andcan have values ranging from +80 to −80: negative values for a denotethe presence of a green component; positive values of a red component;negative values for b denote the presence of a blue component; positivevalues of a yellow component. The colour difference between twomeasurements can be expressed as Cartesian distance between thecoordinates relating to the two measures. Even if this model has not yetsubstituted visual comparison with respect to a standard sample effectedby an expert (mainly during the formulating phase of the colourformulation), it is very useful in the preliminary evaluation of thematerial analyzed and for providing an assessment term in the discussionand comparison with other subjects (such as customers and suppliers).

In addition to the property of colour fastness to light, allhigh-quality synthetic suede leathers, in order to be widely used, musthave a high and long-lasting mechanical resistance. This characteristic,commonly identified as “durability” can be evaluated by subjecting thesynthetic leather to aging according to two types of tests:

-   -   UV aging, carried out in a particular apparatus (Xenotest (3)        under well-defined conditions of relative humidity (20±10%),        temperature (100±3° C.), irradiation (60 W/m²) and time (138        hours), corresponding to a duration cycle of 3 fakra.    -   hydrolyzing aging (Jungle test) carried out in a climatic camera        under well-defined conditions of temperature (75±1° C.),        relative humidity (90±3%) and duration (5-7-10 weeks).

The aging of the material is then analyzed in terms of variation ofappearance, abrasion resistance, variation of the physical-mechanicalproperties and, with respect to the polyurethane matrix only, variationof average Molecular Weights of the polymeric chains.

At present, the objective of a satisfactory durability of syntheticleathers has already been reached by using suitable polyurethanematrices, characterized in that they include “hard” segments, consistingof urethane and/or ureic groups (obtained from the reaction between freeisocyanate groups and water) and “soft” segments consisting of a mixtureof polycarbonate-diols/polyester-diols in a ratio ranging from 80/20 to20/80 (see U.S. Pat. No. 7,144,535).

So far, polyurethane matrices capable of conferring properties of highdurability, have never been used for the production of synthetic leatheralso characterized, by a high colour fastness to light obtained by theaddition of pigments to the molten polymer used for the production ofthe microfibre.

An object of the present invention is to provide a high-qualityartificial leather with a suede appearance mainly intended to use in thefield of car interiors, with colours in the range of grey and black, atthe same time having a high fastness to light and a long durability.

It has been discovered that, by suitably combining the rightquantitative ratios, according to the colour shade to be dyed, the useof carbon black in the micro-fibre, with the possible use of the samecarbon black in the matrix, a polyurethane matrix suitably selected anda tassel length within a well-defined range, it is possible to provide aprocessing intermediate which, when subsequently over-dyed with theaddition of dispersed dyes, in the colours within the grey and blackrange, can produce an artificial leather with a suede appearance capableof complying with the requirements of light fastness, durability,appearance and feel required in the field of car interiors.

The present invention therefore relates a high-quality artificialleather with a suede appearance and within the range of grey and blackcolours, the colour fastness to light, according to the method SAE J1885 225.6 KJ/m² being higher than or equal to 4; the colour fastness tolight, according to the method SAE J 1885 488.8 KJ/m² not being lowerthan 3; said artificial leather having a tassel on the surface of theleather itself; said artificial leather comprising a microfibrous and anelastomeric matrix; the above micro-fibrous component consisting ofpolyester microfibres, preferably of polyethylene terephthalate, havinga count of 0.01 to 0.50 dtex; said elastomeric matrix consisting ofpolyurethane; said polyurethane being made up of soft segments and hardsegments; the ratio between the elastomeric matrix and the micro-fibrouscomponent ranging from 20/80 to 50/50 in mass; the microfibrouscomponent containing the carbon black pigment in a percentage of 0.05 to2.00% in mass, preferably from 0.15 to 1.50%; the elastomeric matrixcontaining the carbon black pigment in a percentage of 0 to 10% byweight, preferably from 0 to 7% by weight, even more preferably from0.02 to 6% by weight; the carbon black always having an averagedimension lower than 0.4 microns; said artificial leather beingcharacterized by:

-   (a) the average length of the tassel ranges from 200 to 500 microns,    preferably from 210 to 400 microns;-   (b) the soft segments consisting of at least one polycarbonate diol    selected from polyalkylene carbonate diols and at least one    polyester diol;-   (c) the hard segments consisting of urethane and/or ureic groups,    the latter deriving from the reaction of free isocyanate groups and    water;-   (d) the total carbon black content ranges from 0.025 to 6% by    weight, preferably from 0.075 to 4.25% by weight, even more    preferably from 0.085 to 3.75% by weight.

The high quality of the artificial leather with a suede appearance ofthe present invention is associated with a complex set oftechnical-sensorial factors among which an evident superficial mottling,a high writing effect, a particularly soft and pleasant feel. Theseeffects are mainly due to the microfibrous component (tassel) of theartificial leather, with particular reference to its surface density andlength, from 200 to 500 microns, preferably from 210 to 400 microns. Anexcessively short and/or low-density tassel, would not allow a completecovering of the polyurethane background, with a consequent qualitativedecrease in the noble surface of the product, from both aesthetical andsensorial point of view. On the other hand, an excessively long tasselwould contribute to reduce the quality of the synthetic leather as itwould be responsible for a “poor” appearance, unlike natural suedeproducts.

Another fundamental characteristic of the artificial leather with asuede appearance of the present invention, is its high aging resistance,capable of lasting for long periods of time, even after long andrepeated exposure to light and to particularly oxidizing and/orhydrolyzing environments, without jeopardizing the characteristic ofsoftness conferred by the microfibrous component. This result has beenobtained by using the particular polyurethanes of the present invention,characterized by soft and hard segments.

The durability of the suede leather of the present invention proves tobe 3 (internal reference photographic standards) in terms of abrasionresistance, after aging under UV rays or after hydrolyzing aging.Furthermore, there is a retention of 80% of the physical-mechanicalcharacteristics after UV aging or hydrolyzing aging.

All these properties are described in more detail in the experimentalsection.

As far as the components of the artificial leather of the presentinvention are concerned, the microfibrous component consists ofmicrofibres of one or more polymers selected from polyethyleneterephthalate, polytrimethylene terephthalate, polybutyleneterephthalate, preferably polyethylene terephthalate.

With respect to the elastomeric matrix, this consists of polyurethane.This term (polyurethane) refers to both real polyurethanes and alsopolyurethane-ureas. The polyurethanes are characterized by the presenceof urethane bonds, formed, for example, by the reaction betweenisocyanate groups and hydroxyl groups, whereas the polyurethane-ureasalso contain ureic bonds obtained, for example, from the reaction ofisocyanate groups and amines or water.

The polyurethanes are made up of soft segments and hard segments. Thesoft segments consist, at least, of one polyalkylene carbonate diol and,of one polyester diol.

Typical examples of polyalkylene carbonate diols are polytetramethylenecarbonate diol (PTMC), polypentamethylene carbonate diol (PPMC),polyhexamethylene carbonate diol (PHC), polyheptamethylene carbonatediol, polyoctamethylene carbonate diol, polynonamethylene carbonatediol, polydeca methylene carbonate diol, poly-(3-methyl-pentamethylenecarbonate) diol (PMPC), poly-(2-methyl-pentamethylene carbonate) diol,poly-(2-methyl-1-octamethylene carbonate) diol.

The polymeric diols used for the synthesis of the polyurethanesdescribed in the examples of the experimental part, normally have anumeral average molecular weight ranging from 1,000 to 3,000, preferablybetween 1,750 and 2,250.

The hard segments refer to portions of polymeric chains deriving fromthe reaction of an organic diisocyanate such as, for example,methylene-bis-(4-phenyl isocyanate) (MDI) or toluene diisocyanate (TDI)with a diamine or glycolic chain. It is in fact well-known that thecompletion of the polyurethane synthesis can be effected by means ofdiamines, thus obtaining polyurethane-ureas, or with glycols, obtaining,in this way, polyurethanes in the true sense.

Diamines possibly used as chain extenders in the production ofpolyurethane-ureas are, among aliphatic diamines, ethylenediamine (EDA),1,3-cyclohexanediamine (1,3-CHDA), 1,4-cyclohexanediamine (1,4-CHDA),isoforondiamine (IPDA), 1,3-propylenediamine (1,3-PDA),2-methylpentamethylenediamine (MPDM), 1,2-propylenediamine (1,2-PDA) andblends thereof. Typical examples of aromatic diamines to be used aschain extenders are 3,3′-dichloro-4,4′-diaminodiphenyl methane,methylene-bis(4-phenyl amine) (MPA), 2,4-diamino-3,5-diethyl toluene,2,4-diamino-3,5-di(methylthio)toluene. The above amines can be added assuch or produced in situ by reaction of the corresponding isocyanate andwater.

The chain extension in polyurethanes in the true sense, can also beobtained with diols such as ethylene glycol, tetramethylene glycol andmixtures thereof. Finally, the chain extension can also be obtained withdicarboxylic acids such as malonic acid, succinic acid, adipic acid.

The hard segments can also include molecules with a hydrophilic natureand/or charged molecules, capable of making the polyurethanes easilydispersible or emulsifiable in water, both in absence and in presence ofexternal surface-active agents. Among molecules having negativelycharged groups capable of facilitating the dispersion of the polymer inwater, 2,2-dimethylol-propanoic acid, 2,2-dimethylol-butanoic acid,compounds functionalized with sulphonic groups, can be mentioned. Amongmolecules having positively charged groups diethanol amine,N-methyl-diethanolamine and, in general, dihydroxy alkyl amines,di-amino-alkyl amines and the salts of quaternary ammonium, can bementioned. Among molecules of a hydrophilic nature, polyoxyalkyl ethersare included.

The reactions used for preparing polyurethanes and polyurethane-ureasare normally carried out in inert, aprotic solvents, such as dimethylacetamide (DMAc), dimethyl formamide (DMF), N-methyl pyrrolidone (NMP),acetone, methyl-ethyl-ketone (MEK). Alternatively, the process can becarried out by dispersing or emulsifying the synthesis intermediates inan aqueous environment or a mixture of water and suitable surface-activeagents; a further alternative of the process can be to synthesize thepolymers or their intermediates in a solvent, subsequently dispersingthe same in water or a mixture of water with suitable surfactants,finally removing the solvent by evaporation.

The polymers thus produced can also be subjected to cross-linking to becarried out in emulsion or dispersion, or after application to thenon-woven fabric, with the purpose of increasing its resistance to theprocess conditions and/or with the purpose of conferring to theimpregnated non-woven fabric, higher resistance characteristics to theaction of atmospheric agents and solvents.

As far as the carbon black is concerned, this pigment is characterizedby the very reduced dimension of its elemental particles (normallysmaller than 0.4 microns) and by their good dispersibility (necessaryfor avoiding an excess aggregation of the same elemental particles, withconsequent fluctuation of the colour and decrease in thephysical-mechanical properties of the polymer). As is known, carbonblack is a black pigment which can be used for conferring colouringswithin the grey/black range to synthetic fibres, whose intensity is inrelation to the concentration of pigment in the polymer and yarn count(denier) of the fibres. In particular, deeper colour shades can beobtained by increasing the percentage of the pigment in the polymerand/or increasing the count of the fibres. The pigment is present in themicrofibrous component in quantities ranging from 0.05 to 2.0% byweight, and it is present in the elastomeric component in a quantity of0 to 10% by weight, in relation to the final colour desired. By changingthe quantity of carbon black in the microfibre and/or in the elastomericportion, it is possible to obtain a large range of colour shades withinlight greys and blacks.

This limit, from the colour point of view, does not effect the field ofcar interiors, a particularly difficult field where high light fastnessis required, but where the chromatic request is strongly concentratedwithin the range of grey and black. Recent data relating to theEuropean, American and Asian markets, indicate the following colourrequests for synthetic leather with a suede appearance:

grey-black shade: 60-80%

beige shade: 15-30%

other shades: 5-10%.

In any case, the total quantity of carbon black in the artificialleather according to the present invention, is from 0.025 to 6%,preferably from 0.075 to 4.25%, even more preferably from 0.085 to 3.75%by weight, otherwise the mechanical properties would decrease.

The present invention also relates to a process of production ofartificial leather with a suede appearance, with colours within therange of grey and black as defined above, comprising the followingsteps:

-   (1) production of a microfibrous intermediate product consisting of    microfibres with the addition of carbon black, said carbon black    being contained in the micro-fibre in a quantity of 0.05% to 2% by    weight, preferably from 0.15 to 1.50% by weight, said microfibres    being selected from microfibres of polyethylene terephthalate,    polytrimethylene terephthalate, polybutylene terephthalate, said    microfibrous intermediate being obtained by the spinning of fibres    obtained by extrusion of a polymer among those indicated above    (defined as island component) with the addition of carbon black,    said carbon black having an average particle-size lower than 0.4    microns, and a binding polymer of the microfibres (sea component)    which is subsequently eliminated during the processing steps by    extraction with an organic solvent;-   (2) impregnation of the microfibrous intermediate product with the    addition of carbon black as per item (1), with a solution and/or    dispersion comprising one or more polyurethanes and carbon black,    the latter being present in a quantity of 0 to 10% by weight,    preferably from 0 to 7% by weight, even more preferably from 0.02 to    6% by weight with respect to the polyurethane, and having an average    particle-size lower than 0.4 microns; the weight ratio between    polyurethane and the microfibrous intermediate ranging from 20/80 to    50/50 in mass; said polyurethane being made up of soft segments and    hard segments, said soft segments consisting of at least one    polyalkylene carbonate diol and at least one polyester diol; said    hard segments consisting of urethane and/or ureic groups deriving    from the reaction between free isocyanate groups and water;    subsequent elimination of the solvent to give a raw semifinished    product;-   (3) grinding of the surface of the above raw semifinished product to    give synthetic leather with the characteristic of a suede    appearance, the length of the tassel of the above-mentioned    synthetic leather being from 200 to 500 μm, preferably from 210 to    400 μm.

Step 1 initially comprises (step 1a) the preparation of a microfibrousintermediate consisting of microfibres of one or more polymers selectedfrom polyethylene terephthalate, polytrimethylene terephthalate,polybutylene terephthalate, preferably polyethylene terephthalate, withthe addition of carbon black. In order to improve the mechanicalproperties of the fibres obtained with the above, these polymers may bepreliminarily subjected to a post-polymerization process in solid state,to increase the length of the polymeric chains.

The production of the microfibres includes the spinning ofmulticomponent fibres by extrusion of a polyester among those mentionedabove (defined as island component) with the addition of carbon black,in percentages ranging from 0.05÷2.00%, preferably 0.15÷1.50% with apolymer binding the microfibres, which is then eliminated during thesubsequent working steps (sea component).

In another preferred embodiment, the production of the above microfibrescan be effected by using a suitable mixture of two polyesters selectedfrom those listed above, one of which, defined as masterbatch, containscarbon black in a percentage ranging from 10 to 50%. To avoidjeopardizing the physical-mechanical properties of the fibre, and makingthe following processing phases difficult, it is preferable for saidmasterbatch to have an Inherent Viscosity value (IV.) not lower than theother polymer one. This can be achieved by subjecting said masterbatchto polymerization in the solid state.

More specifically, the optimum percentages of pigment added to themicrofibre have been selected with the aim of:

-   -   achieving a considerable enhancement in the light fastness;    -   obtaining a wide range of shades between light grey to black        (also using a final over-dyeing treatment of the fibres        themselves);    -   obtaining a high reproducibility of the colour through the        precise definition of the formulations in the final over-dyeing        step;    -   reducing the consumption of dispersed dyes in the over-dyeing        step;    -   minimizing the problems of obstruction of the spinneret;    -   minimizing the fibre types to produce with a different pigment        content (in order to minimize the production costs).

In the most typical cases, the binding polymer (sea component) consistsof polystyrene or a modified polyester or a polymer of the family ofpolyhydroxyalcanoates. The above-mentioned binder must, in any case, beimmiscible with the polymer forming the microfibrous component and mustbe present in percentages between 10-90% by weight (preferably 15-50%).The structure of the microfibre/binder system, is preferably of the“island-sea” type: the overall section of the fibre after spinning(sea+islands) is circular and contains circular islands (micro-fibreswith the addition of carbon black) in its interior, surrounded by thesea (binder) which holds and keeps the islands separate from each other.

As an alternative to the technology described, the fibres, afterspinning, can have elongated or trilobated hollow sections.

The distribution of the bi-component in the section can also be “radial”type (with alternating components “in segments” in a circular section),“skin-core” (with the microfibrous component surrounded by an externalcrown consisting of the binder) or multi-layers (with the two componentsforming parallel and alternating layers).

The fibre collected under the spinneret is then drawn according knowntechnologies and finally crimped and cut in order to produce staplefibre.

The stretching ratio normally applied is within the range of 2.1÷51 Thecrimp number is between 4÷15 per centimetre.

The staple fibre normally has a count within the range of 1.5÷11.0 dtex,preferably between 2.7÷6.7 dtex; a length between 30÷150 mm preferablybetween 30÷100 mm.

An intermediate felt is produced (step 1b) with a non-woven structure,by means of mechanical needle punching or by water jet punching of themicrofibrous intermediate containing carbon black prepared in step (1a).The felt intermediate has density values within the range of 0.150÷0.350g/cm³, typically between 0.150÷0.200 g/cm³ and Unitary Weights withinthe range of 550÷950 g/m², typically between 570÷630 g/m².

The felt intermediate is impregnated according point A3) of the knownproduction method of synthetic leathers with a suede appearance alreadydescribed. The “sea” component of the bi-component fibres is thendissolved according to point A4) of the same production method.

Step 2 consists in the impregnation of the micro-fibrous intermediatecontaining carbon black produced in step 1) with a solution and/ordispersion comprising one or more polyurethanes and, if necessary,carbon black. Said impregnation is effected using one or more solutionsof one or more polyurethanes in organic solvents, for example dimethylformamide. Alternatively, this impregnation can be effected with one ormore polyurethanes in an emulsion or water dispersion. As far as thepolyurethane is concerned, information should be caught in the productclaim.

The subsequent operation consists of eliminating the solvent and/ordispersant and/or emulsifying agent, previously used and eliminating thebinder possibly used in item A3), thus obtaining a “greige” typeintermediate product. The latter is subjected to grinding to “extract”the tassel from the polyurethane matrix in which it has beenimpregnated, in order to confer a microfibre length of 200 to 500microns, preferably from 210 to 400 microns, to the synthetic suedeleather of the present invention.

The suede leather thus obtained can be subjected to a further dyeingstep, preferably effected in a “circular” dyeing apparatus, equippedwith a Venturi nozzle, for example the equipment of Hisaka Works ltd.

The dyeing cycle consists of a first dyeing step, in which the “greige”type intermediate product is put in contact with a mixture of disperseddyes, surface-active agents, which disperse the dye and facilitate itscontact with the fibre, pH conditions suitable for allowing the dye topenetrate inside the same fibre and dyeing auxiliaries. The maximumdyeing temperature, normally between 100÷140° C., is selected so as toheat the polymers forming the micro-fibres above their glass transitiontemperatures, thus facilitating the diffusion of the dye in the polymer.In practice, the “greige” type intermediate is circulated in the dyeingequipment for about 1 hour at the maximum dyeing temperature and,subsequently, subjected to cleaning treatment with sodium hydrosulphitein a basic environment.

A great advantage for the process of the present invention regards thedye amount consumption. With the same final colour (from grey to black)of the suede leather of the present invention, the process describedabove allows a lower consumption of dispersed dyes, because the productto be dyed already has a grey shade due to the presence of carbon black.Furthermore, the lesser use of dispersed dyes (or their total absence)as a result of a colouring due to carbon black, allows the suede leatherof the present invention to have a high colour fastness to light.

For illustrative purposes, a preferred but non-limiting version of theoverall process including the present invention, is schematizedhereunder.

-   B1) Feeding of a mixture consisting of chips of virgin polymer,    typically PET and chips of masterbatch (polymer, typically PET, with    the addition of carbon black) to a spinning line. The masterbatch,    with a high content of carbon black, is quantitatively added to the    virgin polymer so that, downstream of the extrusion process, the    content of the pigment dispersed in the micro-fibrous component is    within the range mentioned above.-   B2) Spinning of a bi-component fibre effected by means of the    well-known spinning technology of the “sea-island” type, wherein the    “sea” component consists of polystyrene and the “island” component    consists of polyethylene terephthalate with the addition of carbon    black. The “islands” thus produced form so-called microfibres “dyed    in mass”, having counts typically falling within the range of    0.10÷0.20 dtex.-   B3) Preparation of an intermediate felt, typically by means of a    mechanical needle punching process, with the fibres obtained as    described in the previous item. The intermediate felt has a    preferable density within the range of 0.150÷0.200 g/cm³ and Unitary    Weights within the range of 580÷630 g/cm².-   B4) Processing of the intermediate felt according to the process    described in items A3-A4-A5-A6-A7-A8 of known high-quality synthetic    suede leathers, with particular attention, in point A8, effecting    the grinding with such conditions able to confer to the microfibre    tassel in the product a length ranging from 200 and 500 microns.-   B5) Final overdyeing of the microfibrous component forming the    synthetic leather with a suede appearance, by means of technologies    traditionally used for the achieving of the desired final colour    shade.

The following examples are provided for a better understanding of thepresent invention.

EXAMPLES

The following table indicates the abbreviations used for identifying theraw materials in the examples

ABBREVIATIONS RAW MATERIAL c.b. Carbon black PET Polyethyleneterephthalate PS Polystyrene PVA Polyvinyl alcohol DMFN,N-Dimethylformamide PHC Polyhexamethylene carbonate glycol PNAPolyneopentyladipate glycol MDI 4-4′ Diphenylmethanediisocyanate DBAN,N-Dibutylamine

Comparative Example 1 (Standard Product)

A bi-component fibre of the “island-sea” type is produced by extruding apair of polymers insoluble with respect to each other.

The polymers used are PET and PS, which are extruded and spun to producea fibre whose sea component consists of PS and the island component PET.The PET has an I.V. value equal to 0.7 dl/g. The fibre thus obtained hasthe following characteristics:

1. Yarn count: 4.2 dtex

2. Length: 51 mm

3. Maximum load strength: 2.08 g/dtex4. Maximum load elongation: 62%5. Crimp number: about 4-5/cm6. PET microfibre strength at maximum load: 3.89 g/dtex7. PET micro-fibre elongation at maximum load: 72%

In particular, the fibre is made up of 57 parts by weight of PET and 43parts by weight of PS. The fibre, if observed in section, reveals thepresence of 16 PET micro-fibres englobed in the PS matrix.

An intermediate felt is prepared with the bi-component fibre, subjectedto needling to form a needled felt having a density within the range of0.180÷0.200 g/cm³ and a Unit Weight within the range of 580÷630 g/m².

The white-coloured needled felt (coordinate CIELAB L equal to 96.3), isimmersed in a water solution at 20% weight of polyvinyl alcohol and thensubjected to drying. The needled felt thus treated is subsequentlyimmersed in trichloroethylene until the complete dissolution of thepolystyrene matrix of the fibres. The non-woven fabric formed is thendried, obtaining an intermediate product called “semifinished product D”(coordinate CIELAB L, after removal of the sea component, equal to96.6).

A polyurethane elastomer is prepared separately, in the form of asolution in DMF. In a first step (pre-polymerization) a solution of PHCand PNA both having a molecular weight of 2,000 in DMF are reacted, at atemperature of 65° C. and under stirring, with MDI in anisocyanate/diols molar ratio of 2.9/1. Three hours after the beginningof the reaction, the pre-polymer thus obtained is cooled to atemperature of 45° C. and diluted with DMF, until a 25% solution ofpre-polymer is obtained having a content of free NCO groups of 1.46%.

DBA and water dissolved in DMF are then slowly added, maintaining atemperature of 45° C., over a period of 5 minutes, in order to have apolyurethane-polyurea having a calculated molecular weight equal to43,000. After heating to 65° C., the reactor is kept under stirring fora further 8 hours obtaining, in the end, a polyurethane-urea solutionwhich is stable with time having a viscosity at 20° C. of 22,000mPa*sec. The elastomer solution thus prepared is then diluted with DMFcontaining Irganox® 1010 and Tinuvin® 326, with the addition of carbonblack in a percentage of 4.8% with respect to PU alone, to form asolution at 14% by weight in PU. The polymer in solution thus obtained,if coagulated with water, is capable of generating structures with ahigh porosity.

The “semifinished product D” is immersed in the solution of thepolyurethane elastomer, squeezed by passage through a pair of rolls andsubsequently immersed in a water bath maintained at 40° C., for onehour. A coagulated semi-finished product is thus obtained which ispassed through a water bath heated to 85° C. to extract the residualsolvent and polyvinyl alcohol. The composite is then dried by passagethrough a heated oven.

The “coagulated and dried semi-finished product” having a thickness of2.30 mm and grey-coloured due to the presence of carbon black in thepolyurethane matrix, is then longitudinally cut to obtain two equallaminates, each having a thickness of 1.15 mm which are then subjectedto grinding to remove an aliquot of the polyurethane matrix, extract themicrofibre component thus forming the tassel. The grinding process iseffected by using suitable abrasive papers under such conditions as toreduce the thickness of the composite material to a value of 0.85 mm,producing a microfibrous tassel having a length of 350÷400 microns(CIELAB L coordinate equal to 55.8).

The composite is finally treated in suitable dyeing machines (“jet”), inorder to dye the microfibre, according to the technology traditionallyused for known synthetic leathers of the suede type, within the grey orblack range. In particular, the composite is passed through the “VenturiTube” for 1 hour, operating at 125° C. in an aqueous dye bath containingthe following dispersed dyes:

Red dispersed dye (anthraquinonic) 5.4% Blue dispersed dye(anthraquinonic) 22.8% Yellow dispersed dye (amino ketone) 9.4%

At the end of the dyeing, a dyed microfibrous non-woven fabric isobtained, which, after further treatment under reducing conditions withsodium hydrosulphite in an alkaline environment to eliminate the excessdye, is subjected to finishing treatment.

The artificial leather thus obtained is subjected to analysis of thephysical-mechanical properties (UNI EN 29073-3) and colour fastness todry and wet rubbing (AATCC 8-2001), to soap washing (AATCC 61-2001), drywashing and light (SAEJ-225.6 KJ/m² and 448.8 KJ/m²).

The evaluations shown in the following tables, relating to the dyedmicrofibrous non-woven product, were effected as follows:

a) for the colour discharge on the test sample (multifibre felt for thewashings and cloth for the rubbings) the dirt on the sample is evaluatedby comparison with the ISO 105A03 grey scale;

b) for the shade exchange of the sample before and after the test, theISO 105A02 grey scale is used.

The evaluation is effected by comparing the shade exchange or the dirtylevel with the shade contrasts codified by the appropriate grey scale;an evaluation equal to 5 corresponds to no change in shade/colourtransfer, whereas an evaluation of 1 corresponds to the maximum contrastfound on the grey scale used.

TEST Evaluation Longitudinal ultimate tensile strength 410 N Transversalultimate tensile strength 310 N Longitudinal elongation at 50 N  4.9%Transversal elongation at 50 N 20.0% Wet rubbing AATCC 8-2001 (colourdischarge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5 Soapwashing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 3/4 Dry washing (shade exchange) 5 Dry washing(colour discharge) 3/4 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 3 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange) 2/3

Example 2 (Fast Colour from Master SSP with 1% c.b.in Fibre)

A masterbatch consisting of PET chips with the addition of carbon blackat 30% by weight, is polymerized in the solid state in order to increaseits Inherent viscosity (I.V.).

Polymerization is effected in the solid state (SSP) at a temperature of203° C. and a pressure of 42 mbar for 100 hours.

The trend of the SSP process is controlled by I.V. measurements effectedby means of the following analytic method: 0.5 g of masterbatch arefinely ground with a specific “grinding mill”, and immersed in a 50 ccsolution of dichloroacetic acid, maintaining them at 85° C. for 6 hoursand subsequently at 70° C. in an ultrasound bath for a further 30minutes in order to complete the dissolution of the polymer. Thesolution thus obtained is then analyzed by means of a capillaryviscometer of the “Ostwald” type.

By comparing the flow time used by the solution to cover a certainportion of the capillary with the time used by the solvent alone, thevalue of the specific viscosity is obtained. The I.V. value is obtainedfrom the latter value using appropriate mathematical formulae.

The I.V. before and after the SSP treatment is obtained by means of theabove method. The results are as follows:

-   -   I.V. masterbatch as such=0.35 dl/g    -   I.V. masterbatch after SSP=0.71 dl/g

The chips of masterbatch polymerized in the solid state are then addedand suitably mixed, in a proportion of 1/30, with virgin PET chips (I.V.equal to 0.7 dl/g).

The chips thus mixed are then extruded and spun together with a quantityof PS, according to the procedure of the “sea-island” spinningtechnology, to produce a bi-component fibre whose “sea” componentconsists of PS and the island component consists of PET with theaddition of c.b. The fibre thus obtained has the followingcharacteristics:

1. Yarn count (denier): 4.2 dtex

2. Length: 51 mm

3. Maximum load strength: 2.18 g/tex

4. Maximum load elongation: 70%

5. Crimp number: about 4-5/cm

6. PET microfibre strength under maximum load: 3.86 g/dtex

7 Elongation of the PET microfibre under maximum load: 68%.

In particular, the fibre consists of 57 parts by weight of PET with theaddition of carbon black and 43 parts by weight of PS. When observed insection, the fibre reveals the presence of 16 micro-fibres of“PET+carbon black” englobed in the PS matrix.

An intermediate felt is prepared with the bi-component fibre and issubjected to needling to form a needled felt having a density within therange of 0.170÷0.190 c/cm³ and Unitary Weights within the range of580÷630 g/m².

The needled felt, having a dark grey colour due to the presence of thefibre with the addition of carbon black (CIELAB L coordinate equal to35.7), is immersed in an aqueous solution at 20% by weight and thensubjected to drying.

The needled felt thus treated is subsequently immersed intrichloroethylene until the complete dissolution of the polystyrenematrix of the fibres. The non-woven fabric thus formed is then dried,obtaining an intermediate product called “semi-finished product D”(CIELAB L coordinate, after removal of the sea component, equal to40.1).

A polyurethane elastomer is prepared separately, as already described inexample 1. The elastomer solution thus prepared is then diluted with DMFcontaining Irganox® 1010 and Tinuvin® 326, with the addition of carbonblack in a percentage of 4.8% with respect to the PU alone, to form asolution in PU at 14% by weight. The polymer in solution thus obtained,if coagulated in water, is capable of generating structures with highporosities.

The “semi-finished product D” is immersed in the solution of thepolyurethane elastomer squeezed by passing it through a pair of rollsand subsequently immersed for 1 hour in a water bath maintained at 40°C. A coagulated semifinished product is thus obtained which is passedthrough a water bath heated to 85° C. to extract the residual solventand polyvinyl alcohol. The composite material is then dried by passingit through a heated oven.

The “coagulated and dried semifinished product”, having a thickness of2.30 mm and a dark grey colour due to the presence of carbon black bothin the fibre and in the polyurethane matrix, is then longitudinally cutto obtain two equal laminates, each having a thickness of 1.15 mm whichare then subjected to grinding to remove an aliquot of the polyurethanematrix, to extract the microfibre component thus forming the tassel. Thegrinding process is effected using specific abrasive papers under suchconditions as to reduce the thickness of the composite material to avalue of 0.85 mm, producing a microfibrous tassel having a length of350÷400 microns (CIELAB L coordinate equal to 33.8).

The composite is finally treated in suitable dyeing machines (“jet”), inorder to over-dye the microfibre with the addition of carbon black,according to the technology traditionally used for known syntheticleathers, to give a suede type leather, coloured within the range ofgrey or black. In particular, the composite is passed through the“Venturi Tube” for 1 hour, operating at 125° C. in an aqueous dyeingbath containing the following dispersed dyes:

Red dispersed dye (anthraquinonic) 4% Blue dispersed dye(anthraquinonic) 3% Yellow dispersed dye (amino ketone) 3.5% 

At the end of the dyeing, a dyed microfibrous non-woven product isobtained, which, after further treatment under reducing conditions withsodium hydrosulphite in an alkaline environment to eliminate the excessdye, is subjected to finishing treatment.

The artificial leather thus obtained is subjected to analysis of thephysical-mechanical properties and colour fastness, to rubbing, soapwashing and a combination of dry washing and light exposure as widelydescribed in example 1. The evaluations are shown in the following table

TEST Valutazione Longitudinal ultimate tensile strength 450 NTransversal ultimate tensile strength 248 N Longitudinal elongation at50 N  4.5% Transversal elongation at 50 N 24.0% Wet rubbing AATCC 8-2001(colour discharge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5Soap washing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 4/5 Dry washing (shade exchange) 5 Dry washing(colour discharge) 4/5 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 4/5 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange) 4

Example 3 (Fast Colour from Master SSP with 0.4% c. b. In Fibre andLighter Dyeing-Shade Colour)

The chips of masterbatch polymerized in the solid state as described inexample 2, are added and suitably mixed to chips of virgin PET (I.V.equal to 0.7 dl/g), in a proportion of 1/75.

The chips thus mixed are then extruded and spun together with PS,according to the procedure of the “sea-island” spinning technology, toproduce a bi-component fibre, whose “sea” component consists of PS andthe island component consists of PET with the addition of c.b. The fibrethus obtained has the following characteristics:

1. Yarn count (denier): 4.2 dtex

2. Length: 51 mm

3. Maximum load strength: 2.09 g/tex

4. Maximum load elongation: 71%

5. Crimp number: about 4-5/cm

6. PET microfibre strength under maximum load: 3.84 g/dtex

7 Elongation of the PET microfibre under maximum load: 74%.

In particular, the fibre consists of 57 parts by weight of PET with theaddition of carbon black and 43 parts by weight of PS. When observed insection, the fibre reveals the presence of 16 micro-fibres of“PET+carbon black” englobed in the PS matrix.

An intermediate felt is prepared with the bi-component fibre and issubjected to needling to form a needled felt having a density within therange of 0.204÷0.208 c/cm³ and Unitary Weights within the range of550÷580 g/m².

The needled felt, having a dark grey colour due to the presence of thefibre containing carbon black (CIELAB L coordinate equal to 50.4), isimmersed in an aqueous solution at 20% by weight and then subjected todrying.

The needled felt thus treated is subsequently immersed intrichloroethylene until the complete dissolution of the polystyrenematrix of the fibres. The non-woven fabric thus formed is then dried,obtaining an intermediate product called “semi-finished product D”(CIELAB L coordinate, after removal of the sea component, equal to51.6).

A polyurethane elastomer is prepared separately, as already described inexample 1. The elastomer solution thus prepared is then diluted with DMFcontaining Irganox® 1010 and Tinuvin® 326, with the addition of carbonblack in a percentage of 0.3% with respect to the PU alone, to form asolution in PU at 14% by weight The polymer in solution thus obtained,if coagulated in water, is capable of generating structures with highporosities.

The “semi-finished product D” is immersed in the solution of thepolyurethane elastomer squeezed by passing it through a pair of rollsand subsequently immersed for 1 hour in a water bath maintained at 40°C. A coagulated semifinished product is thus obtained which is passedthrough a water bath heated to 85° C. to extract the residual solventand polyvinyl alcohol. The composite material is then dried by passingit through a heated oven.

The “coagulated and dried semifinished product”, having a thickness of2.30 mm and a dark grey colour due to the presence of carbon black bothin the fibre and in the polyurethane matrix, is then longitudinally cutto obtain two equal laminates, each having a thickness of 1.15 mm whichare then subjected to grinding to remove an aliquot of the polyurethanematrix, extract the microfibre component and thus form the tassel. Thegrinding process is effected by using specific abrasive papers undersuch conditions as to reduce the thickness of the composite material toa value of 0.85 mm, producing a microfibrous tassel having a length of300÷350 microns (CIELAB L coordinate equal to 50.0).

The composite is finally treated in suitable dyeing machines (“jet”), inorder to over-dye the microfibre containing carbon black, according tothe technology traditionally used for known synthetic leathers, to givea suede-type leather, coloured within the grey or black range.

Unlike what has been observed with the composite materials previouslyillustrated, the lower amount of carbon black used makes it necessary touse a higher quantity of dyes, if the final colour desired is the same.Starting from a lighter grey shade, on the contrary, a range of lightercolours can be obtained, by over-dyeing, which would otherwise beimpossible to produce starting from the grey base of the compositepreviously illustrated (example 2), in any case maintaining equally highcolour fastness performances.

In particular, the composite is passed through the “Venturi Tube” for 1hour, operating at 125° C. in an aqueous dyeing bath containing thefollowing dispersed colours:

Red dispersed dye (anthraquinonic) 0.7% Blue dispersed dye(anthraquinonic) 1.9% Yellow dispersed dye (amino ketone) 0.5%

At the end of the dyeing, a dyed microfibrous non-woven fabric isobtained, which, after further treatment under reducing conditions withsodium hydrosulphite in an alkaline environment to eliminate the excessdye, is subjected to finishing treatment. The artificial leather thusobtained is subjected to analysis of the physical-mechanical propertiesand colour fastness to rubbing, soap washing and a combination of drywashing and light exposure as widely described in example 1. Theevaluations are indicated in the following table

TEST Valutazione Longitudinal ultimate tensile strength 410 NTransversal ultimate tensile strength 240 N Longitudinal elongation at50 N  5.5% Transversal elongation at 50 N 25.0% Wet rubbing AATCC 8-2001(colour discharge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5Soap washing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 4/5 Dry washing (shade exchange) 5 Dry washing(colour discharge) 4/5 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 4/5 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange) 4

By comparison, a composite produced with the same procedure, startinghowever from virgin PET fibres (with no addition of carbon black),required, in order to obtain the same colour shade, the use of a dyeingbath with the following dispersed dyes

Red dispersed dye (anthraquinonic) 1.3% Blue dispersed dye(anthraquinonic) 3.8% Yellow dispersed dye (amino ketone) 1.3%

Example 4—(Non-Regraded Fast Colour with 1% Carbon Black in Fibre)

The chips of masterbatch as such (containing PET with the addition ofcarbon black at 30% by weight, I.V. equal to 0.35 dl/g), are added toand suitably mixed, in a proportion of 1/30, with chips of virgin PET(I.V. of 0.7 dl/g).

The chips thus mixed are then extruded and spun together with PS,according to the “sea-island” spinning technology, to produce abi-component fibre, whose sea component consists of PS and the islandcomponent consists of PET with the addition of carbon black. The fibrethus obtained has the following characteristics:

1. Yarn count (denier): 4.2 dtex

2. Length: 51 mm

3. Maximum load strength: 1.45 g/tex

4. Maximum load elongation: 69%

5. Crimp number: about 4-5/cm

6. PET microfibre strength under maximum load: 2.55 g/dtex

7 Elongation of the PET microfibre under maximum load: 72%.

In particular, the fibre consists of 57 parts by weight of PET with theaddition of carbon black and 43 parts by weight of PS. When observed insection, the fibre reveals the presence of 16 micro-fibres of“PET+carbon black” englobed in the PS matrix.

An intermediate felt is prepared with the bi-component fibre and issubjected to needling to form a needled felt having a density within therange of 0.240÷0.260 c/cm³ and Unitary Weights within the range of630÷650 g/m². Also during the production of the felt, problems wereobserved relating to the breakage of the microfibre, which causes asudden increase in density and frequent needle breaks.

The needled felt, having a dark-grey colour due to the presence of thefibre with the addition of carbon black (CIELAB L coordinate equal to35.4), is immersed in an aqueous solution of polyvinyl alcohol at 20% byweight and then subjected to drying.

The needled felt thus treated is subsequently immersed intrichloroethylene until the complete dissolution of the polystyrenematrix of the fibres. The non-woven fabric thus formed is then dried,obtaining an intermediate product called “semi-finished product D”(CIELAB L coordinate, after removal of the sea component, equal to40.3).

A polyurethane elastomer is prepared separately, as already described inexample 1. The elastomer solution thus prepared is then diluted with DMFcontaining Irganox® 1010 and Tinuvin® 326, with the addition of carbonblack in a percentage of 4.8% with respect to the PU alone, to form asolution in PU at 14% by weight. The polymer in solution thus obtained,if coagulated in water, is capable of generating structures with highporosities.

The “semi-finished product D” is immersed in the solution of thepolyurethane elastomer, squeezed by passing it through a couple of rollsand subsequently immersed for 1 hour in a water bath maintained at 40°C. A coagulated semifinished product is thus obtained which is passedthrough a water bath heated to 85° C. to extract the residual solventand polyvinyl alcohol. The composite material is then dried by passingit through a heated oven.

The “coagulated and dried semifinished product”, having a thickness of2.30 mm and a dark grey colour due to the presence of carbon black bothin the fibre and in the polyurethane matrix, is then longitudinally cutto obtain two equal laminates, each having a thickness of 1.15 mm whichare then subjected to grinding to remove an aliquot of the polyurethanematrix, extract the microfibre component and thus form the tassel. Thegrinding process is effected by using suitable abrasive papers undersuch conditions as to reduce the thickness of the composite material toa value of 0.85 mm, producing a microfibrous tassel having a length of320÷370 microns (CIELAB L coordinate equal to 34.0).

The composite is finally treated in suitable dyeing machines (“jet”), inorder to over-dye the microfibre containing carbon black, according tothe technology traditionally used for known synthetic leathers, to givea suede-type leather, coloured within the grey or black range. Inparticular, the composite is passed through the “Venturi Tube” for 1hour, operating at 125° C. in an aqueous dyeing bath containing thefollowing dispersed colours:

Red dispersed dye (anthraquinonic) 4% Blue dispersed dye(anthraquinonic) 3% Yellow dispersed dye (amino ketone) 3.5% 

At the end of the dyeing, a dyed microfibrous non-woven fabric isobtained, which, after further treatment under reducing conditions withsodium hydrosulphite in an alkaline environment to eliminate the excessdye, is subjected to finishing treatment.

The artificial leather thus obtained is subjected to analysis of thephysical-mechanical properties and colour fastness to rubbing, soapwashing and a combination of dry washing and light exposure as widelydescribed in example 1. The evaluations are indicated in the followingtable

TEST Evaluation Longitudinal ultimate tensile strength 424 N Transversalultimate tensile strength 272 N Longitudinal elongation at 50 N  3.6%Transversal elongation at 50 N 22.0% Wet rubbing AATCC 8-2001 (colourdischarge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5 Soapwashing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 4/5 Dry washing (shade exchange) 5 Dry washing(colour discharge) 4/5 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 4/5 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange) 4

The composite has a thickness of 0.82 mm.

Example 5 (Non-Regraded Fast Colour with 2% Carbon Black in Fibre)

The chips of masterbatch as such (containing PET with the addition of30% by weight of carbon black, I.V. equal to 0.35 dl/g), are added toand suitably mixed, in a proportion of 1/15, with chips of virgin PET(I.V. of 0.7 dl/g).

The chips thus mixed are then extruded and spun together with PS,according to the “sea-island” spinning technology, to produce abi-component fibre, whose sea component consists of PS and the islandcomponent consists of PET with the addition of carbon black. The fibrethus obtained has the following characteristics:

1. Yarn count (denier): 4.2 dtex

2. Length: 51 mm

3. Maximum load strength: 1.4 g/tex

4. Maximum load elongation: 62%

5. Crimp number: about 4-5/cm

6. PET microfibre strength under maximum load: 2.52 g/dtex

7. Elongation of the PET microfibre under maximum load: 72%.

In particular, the fibre consists of 57 parts by weight of PETcontaining carbon black and 43 parts by weight of PS. When observed insection, the fibre reveals the presence of 16 microfibres of “PET+carbonblack” englobed in the PS matrix.

An intermediate felt is prepared with the bi-component fibre and issubjected to needling to form a needled felt having a density within therange of 0.240÷0.260 c/cm³ and Unitary Weights within the range of615÷630 g/m².

The needled felt, having a dark grey colour due to the presence of thefibre containing carbon black (CIELAB L coordinate equal to 25.0), isimmersed in an aqueous solution of polyvinyl alcohol at 20% by weightand then subjected to drying.

The needled felt thus treated is subsequently immersed intrichloroethylene until the complete dissolution of the polystyrenematrix of the fibres. The non-woven fabric thus formed is then dried,obtaining an intermediate product called “semi-finished product D”(CIELAB L coordinate, after removal of the sea component, equal to30.3).

A polyurethane elastomer is prepared separately, as already described inexample 1. The elastomer solution thus prepared is then diluted with DMFcontaining Irganox® 1010 and Tinuvin® 326, with the addition of carbonblack in a percentage of 4.8% with respect to the PU alone, to form asolution in PU at 14% by weight. The polymer in solution thus obtained,if coagulated in water, is capable of generating structures with highporosities.

The “semi-finished product D” is immersed in the solution of thepolyurethane elastomer, squeezed by passing it through a pair of rollsand subsequently immersed for 1 hour in a water bath maintained at 40°C. A coagulated semifinished product is thus obtained which is passedthrough a water bath heated to 85° C. to extract the residual solventand polyvinyl alcohol. The composite material is then dried by passingit through a heated oven.

The “coagulated and dried semifinished product”, having a thickness of2.30 mm and dark-grey colour due to the presence of carbon black both inthe fibre and in the polyurethane matrix, is then longitudinally cut toobtain two equal laminates, each having a thickness of 1.15 mm which arethen subjected to grinding to remove an aliquot of the polyurethanematrix, extract the microfibrous component and thus form the tassel. Thegrinding process is effected by using suitable abrasive papers undersuch conditions as to reduce the thickness of the composite material toa value of 0.85 mm, producing a microfibrous tassel having a length of320÷370 microns (CIELAB L coordinate equal to 24.4).

The composite is finally treated in suitable dyeing machines (“jet”) inorder to over-dye the microfibre containing carbon black, according tothe technology traditionally used for already known synthetic leathers,to give a suede-type leather coloured within the grey and black range.

Unlike what has been observed with the composite products describedabove, the higher quantity of carbon black used does not allow the samecolour range to be reproduced, starting from the composite productsalready described. The colours listed in the following table, forexample, characterized by high sales volumes, cannot be preparedstarting from the present composite product due to the greaterbrightness of the colour shade required with respect to that of thecomposite produced (CIELAB L coordinate equal to 24.4)

Colour L 6650 29.86 6750 26.89 6950 32.87

For other colours, on the other hand, difficulties are observed forreaching the desired colour shade by means of over-dyeing due to thestrong colour changes towards red and/or blue shades of the compositeproduct and to the poor contribution of the dyes necessary for effectingthe shade correction. The smaller colour range which can be developed onthis colour base of the composite product, however, is coupled by astrong increase in resistance on particularly dark colours (black inparticular) which in any case require considerable additions of dyeseven when starting from the composite product described in examples 2and 4.

In particular, the composite is passed through the “Venturi Tube” for 1hour, operating at 125° C. in an aqueous dyeing bath containing thefollowing dispersed dyes:

Red dispersed dye (anthraquinonic) 1% Blue dispersed dye(anthraquinonic) 3% Yellow dispersed dye (amino ketone) 10.5%  

At the end of the dyeing, a dyed microfibrous non-woven fabric isobtained, which, after further treatment under reducing conditions withsodium hydrosulphite in an alkaline environment to eliminate the excessdye, is subjected to finishing treatment.

The artificial leather thus obtained is subjected to analysis of thephysical-mechanical properties and colour fastness to rubbing, soapwashing and the combination of dry washing and light exposure as widelydescribed in example 1. The evaluations are indicated in the followingtable

TEST Evaluation Longitudinal ultimate tensile strength 395 N Transversalultimate tensile strength 240 N Longitudinal elongation at 50 N  7.0%Transversal elongation at 50 N 32.0% Wet rubbing AATCC 8-2001 (colourdischarge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5 Soapwashing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 4/5 Dry washing (shade exchange) 5 Dry washing(colour discharge) 4/5 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 4/5 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange)4/5

PET fibre (with no addition of carbon black) required, in order toobtain the same colour shade, the use of a dyeing bath with thefollowing dispersed dyes:

Red dispersed dye (anthraquinonic) 5.7% Blue dispersed dye(anthraquinonic) 12.8% Yellow dispersed dye (amino ketone) 18.1%

Comparative Example 6 (Fast Colour from Master SSP with 1% Carbon Blackin Fibre and Short Tassel)

The composite product, prepared as described in example 2, was groundunder such conditions as to produce a micro-fibrous tassel having alength ranging from 90 to 120 μm (CIELAB L coordinate equal to 33.4).

The composite is finally treated in suitable dyeing machines (“jet”), inorder to over-dye the microfibre containing carbon black, according tothe technology traditionally used for known synthetic leathers of thesuede type, within the range of grey or black. In particular, thecomposite is passed through the “Venturi Tube” for 1 hour, operating at125° C. in an aqueous dyeing bath containing the following disperseddyes:

Red dispersed dye (anthraquinonic) 3.8% Blue dispersed dye(anthraquinonic) 2.8% Yellow dispersed dye (amino ketone) 3.2%

At the end of the dyeing, a dyed microfibrous non-woven is obtained,which, after further treatment under reducing conditions with sodiumhydrosulphite in an alkaline environment to eliminate the excess dye, issubjected to finishing treatment.

The artificial leather thus obtained shows an evident qualitative decayfrom an aesthetical point of view due to the excessive exposure of thepolyurethane background and to the loss of the writing and marblingeffect caused by the particularly short microfibrous tassel. Prototypesof composite products thus produced were considered as being unsuitableby the final user and therefore discarded.

The evaluation of the physical-mechanical properties and colourresistance tests to rubbing, soap washing and a combination of drywashings and light exposures (already widely described in example 1),are indicated in the following table

TEST Evaluation Longitudinal ultimate tensile strength 445 N Transversalultimate tensile strength 250 N Longitudinal elongation at 50 N  4.3%Transversal elongation at 50 N 23.0% Wet rubbing AATCC 8-2001 (colourdischarge) 4 Dry rubbing AATCC 8-2001 (colour discharge) 4/5 Soapwashing AATCC 61-2001 (colour exchange) 5 Dry washing AATCC 61-2001(colour discharge) 4/5 Dry washing (shade exchange) 5 Dry washing(colour discharge) 4/5 Light fastness, SAE J 1885 225.6 KJ/m² (shadeexchange) 4/5 Light fastness, SAE J 1885 488.8 KJ/m² (shade exchange) 4

The composite product has a thickness of 0.78 mm.

Summarazing Table

The main characteristics of the composite materials described above aresummarized hereunder, for a clearer and more convenient reading.

Comparative example 1 refers to the production of artificial suedeleather with no carbon black in the micro-fibrous part.

Comparative example 6 refers to the production of suede leather having atassel length of 90-120 microns.

TEST 1C 2 3 4 5 6C I.V. masterbatch (dl/g) — 0.71 0.71 0.35 0.35 0.71c.b. microfibre content (%) 0 1 0.4 1 2 1 c.b. elastomer content (%) 4.84.8 0.3 4.8 4.8 4.8 c.b. total content (%) 1.6 2.3 0.4 2.3 2.9 2.3 fibrecount (dtex) 4.2 4.2 4.2 4.2 4.2 4.2 fibre toughness (g/dtex) 2.08 2.182.09 1.45 1.40 2.18 fibre elongation (%) 62 70 71 69 62 70 PETmicrofibre toughness 3.89 3.86 3.84 2.55 2.52 3.86 (g/dtex) PETmicrofibre elongation 72 68 74 72 72 68 (%) felt luminosity (L) 96.335.7 50.4 35.4 25.0 35.7 composite luminosity (L) 55.8 33.8 50.0 34.024.4 33.4 tassel length (μm) 350-400 320-370 300-350 320-370 320-37090-120 Fastness to light, SAE J 1885 3 4/5 4 (4/5*) 4/5 (4/5*) 4/5 225.6KJ/m² (shade exchange) Fastness to light, SAE J 1885 2/3 4 3/4 (4*)   4(4/5*) 4 488.8 KJ/m² (shade exchange) increase in the colour fastness ofthe dye to light, even of 1-1.5 with respect to the grey scale (seeexamples 1C and 2); by increasing the carbon black content in the fibre,the colour fastness to light increases but the colour range which can beobtained starting from the intermediate microfibrous compound decreases(decrease in the luminosity value L of the same intermediate product);the addition of masterbatch containing carbon black causes a slightdecrease in the physical-mechanical properties of the fibre; themasterbatch polymerization process in the solid state (see examples 2and 3) allows the production of a microfibre with improved mechanicalproperties, comparable with that of the reference product, withoutcarbon black, described in comparative example 1.

We claim:
 1. A non-woven artificial leather, having a suede appearance,said non-woven artificial leather consisting essentially of a non-wovenmicrofibrous component and an elastomeric matrix; the non-wovenmicrofibrous component comprising polyester microfibres having a countof 0.01 to 0.50 dtex and carbon black pigment in a percentage of 0.05 to2.00% by weight; the elastomeric matrix comprising polyurethanecomprising soft and hard segments and carbon black pigment in apercentage of 0 to 10% by weight; wherein the soft segments comprise atleast one polycarbonate diol selected from polyalkylene carbonate diols,and at least one polyester diol; wherein the hard segments compriseurethane groups deriving from the reaction between free isocyanategroups and water; and wherein part of the microfibrous component formstassels on a surface of the artificial leather having an average lengthranging from 210 to 400 microns, which provides an improved mottlingeffect and writing effect.
 2. The artificial leather according to claim1, wherein the microfibrous component comprise polyethyleneterephthalate microfibres.
 3. The artificial leather according to claim1, wherein the polyester microfibres contain carbon black in apercentage of 0.15 to 1.50% by weight.
 4. The artificial leatheraccording to claim 1, wherein the elastomeric matrix contains the carbonblack pigment in a percentage ranging from 0 to 7% by weight.
 5. Theartificial leather according to claim 1, wherein the elastomeric matrixcomprises the carbon black pigment in a percentage ranging from 0.02% to10% by weight.
 6. The artificial leather according to claim 1, whereinthe elastomeric matrix comprises the carbon black pigment in apercentage ranging from 0.02% to 7% by weight.
 7. The artificial leatheraccording to claim 1, wherein the elastomeric matrix comprises thecarbon black pigment in a percentage ranging from 0.02% to 6% by weight.8. The artificial leather according to claim 1, wherein the overallcontent of carbon black ranges from 0.075 to 4.25% by weight.
 9. Theartificial leather according to claim 1, wherein the overall content ofcarbon black ranges from 0.025 to 6% by weight.
 10. The artificialleather according to claim 1, wherein the overall content of carbonblack ranges from 0.085 to 3.75% by weight.
 11. The artificial leatheraccording to claim 1, wherein the carbon black has an average dimensionlower than 0.4 microns.
 12. The artificial leather according to claim 1having a color shade within the grey-black range, wherein the lightfastness of the color shade being higher than or equal to 4, accordingto the method SAE J 1885 225.6 KJ/m², and not lower than 3, according tothe method SAE J 1885 488.8 KJ/m².
 13. The artificial leather accordingto claim 1, wherein the polyester diols are selected from the groupconsisting of polyhexamethylene adipate diol (PHA),poly(3-methylpentamethylene) adipate diol (PMPA), polyneopentyl adipatediol (PNA), and polycaprolactone diol (PCL); the polyalkylenecarbonatediols are selected from the group consisting of polytetramethylenecarbonate diol (PTMC), polypentamethylene carbonate diol (PPMC),polyhexamethylene carbonate diol (PHC), polyheptamethylene carbonatediol, polyoctamethylene carbonate diol, polynonamethylene carbonatediol, polydecamethylene carbonate diol, poly-(2-methyl-pentamethylenecarbonate)diol, and poly-(2-methyl-1-octamethylene carbonate) diol; andthe isocyanate groups are derived frommethylene-bis-(4-phenylisocyanate) (MDI) and/or from toluenediisocyanate (TDI).
 14. The artificial leather according to claim 1,wherein the color shade is characterized by a value of “L”<70, whereinsaid value is measured before the artificial leather is subjected to anover-dyeing treatment.
 15. The artificial leather according to claim 14,wherein the color shade is characterized by a value of “L”<55.
 16. Theartificial leather according to claim 1, wherein the polyester diol ispolyhexamethylene adipate diol (PHA).
 17. The artificial leatheraccording to claim 1, wherein the hard segment of said polyurethanefurther comprises one or more compounds selected from the groupconsisting of 2,2-dimethylol-propanoic acid, 2,2-dimethylol-butanoicacid, N-methyl-diethanolamine, dihydroxy alkyl amines, di-amino-alkylamines, quaternary ammonium salts, and polyoxyalkyl ethers.
 18. Theartificial leather according to claim 1, wherein the tassels on thesurface of the artificial leather have an average length ranging from210 to 370 microns.
 19. The artificial leather according to claim 1,wherein the tassels on the surface of the artificial leather have anaverage length ranging from 210 to 350 microns.